Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a medium for generating a raster image. In particular, the present invention relates to image processing accompanied by combining and is suitable to rendering of a raster image.
Description of the Related Art
Combining processing in rendering is processing to form an image as the results of combining a front image and a rear image. As one example, according to the Porter-Duff rules described in “Compositing Digital Images” (T. Porter and T. Duff, Computer Graphics, vol. 18, No. 3, ACM 1984), 12 compositing operators (combining operators) are systematized to be capable of show-through compositing (combining). As another example, in “Document management—Portable document format—Part 1: PDF 1.7” (Adobe Systems, ISO 32000-1, 2008), a method of simultaneously performing show-through combining of a set of continuous objects called Transparency Groups of PDF (Portable Document Format) is specified. The set of continuous objects (in the present specification, described as a “group”) may have another group as an element. That a group has another group as an element means that the group has a nest structure. In the present specification, an element of a group is described as a “group element”
As a technique related to rendering, there is known a technique to make an attempt to reduce data size, in the case where intermediate data has overflowed a memory area for storing the intermediate data, by temporarily performing rendering of the intermediate data at the point of time of the overflow (see Japanese Patent Laid-Open No. 2011-61555). Making an attempt to reduce data size by, in particular, combining processing in this technique is described as “flattening” in the present specification.